The present invention generally relates to a downhole gauge package integrated into a delivery and communications cable. More particularly, the present invention relates to a downhole gauge package integrated into a communications cable requiring no assembly and having a single uniform outer diameter.
Downhole sensor gauges are used throughout the petroleum drilling and recovery industry to measure and report various downhole conditions. Gauges that record and measure temperature, pressure, and other types of information are deployed to a location of interest downhole for either long or short-term emplacement. Particularly, one form of long-term emplacement involves the installation of a gauge below a packer to report a condition below the packer back to a remote location. Packers are frequently installed in petroleum industry wellbore to isolate one zone or region from another, adjacent zone or region. Particularly, packers can be used in petroleum production to isolate the annulus between a string of production tubing and a cased borehole to prevent the unwanted escape of production fluids.
Packers typically perform their functions by expanding an elastomeric packer element to fill any gaps between the production tube and the cased borehole. The packer element can be expanded by “inflating” the element with pressurized fluid or by activating the flexible element by axially compressing it between two pistons. Irrespective of construction or the deployment method used, the packer effectively creates a fluid seal between the production tubing and the remainder of the borehole.
However, while a production zone is isolated by a packer, downhole condition measurements are still necessary to determine the status of the isolated zone. While gauges (e.g. Temperature sensors and pressure transducers) can be deployed to the production zone through the bore of production tubing running through the packer, it is not preferred. Sensors that run through the production tubing bore can restrict the flow of production fluids or can interfere with the operation of production equipment located at the distal end of the production tubing. Furthermore, various pieces of equipment, for example downhole safety valves, require an unobstructed bore to be effective or to be in compliance with regulations.
To accommodate sensor gauges, packer designs have formerly been produced that allow a conduit to pass through the production tubing-casing annulus and bypass the packer element. These former designs typically involve a port through the body of the packer through which a constant diameter communications conduit can pass. Seals inside the port seal with the outer profile of the communications conduit and therefore prevent fluids from escaping from or invading into the production zone. Because of the design of the seals, the communications conduit has to be of a substantially consistent outer profile. Irregularities in the outer profile of the communications conduit can prevent a proper seal with the packer, thereby compromising the packer's function to isolate upper and lower borehole zones.
Former downhole gauge systems required the passage of the conduit through the port of the packer assembly followed by the attachment and connection of the gauge device to the distal end of the communications conduit once the packer was traversed. This was necessary because either the gauge assembly or the connection means between the conduit and the gauge typically had an outer profile that was larger than the communications conduit itself. The larger profiled gauge or connection means was unable to pass through the communications port designed to hydraulically seal against the smaller, more consistent communications conduit. Therefore, the communications conduit and the gauge assembly were typically delivered to the field location separately. Any functional checks that needed to be made on the gauge had to be performed prior to its final mating with the communications conduit and at the field location. As a result there was no way to test the integrity of the final conduit/gauge communications interface until after the gauge was installed below the packer, when a repair or replacement operation would be very costly.